[Pw_forum] High Ecut for Ultrasoft PPs

[Zarah Baiyee]

Dear Nicola,

Thanks very much for this clarification and information, it is a massive
help.

Kind Regards

Zarah


On Wed, Apr 16, 2014 at 6:27 PM, Nicola Marzari <nicola.marzari at epfl.ch>wrote:

> On 16/04/2014 11:29, Zarah Baiyee wrote:
> > Dear all,
> >
> > I am studying a BaFeO3 perovskite structure, and I am struggling with
> > the convergence, primarily the Ecut WFC convergence.
> >
> > So far I have used a variety of PPs for this structure, yet cannot get a
> > sensible convergence for the Ecut Wfc, please see my convergence data
> > below:
>
>
>
> Dear Zarah,
>
>
> 1) you do not check cutoff convergence on the total energy,
> but on its derivtives: forces for a distorted configuration,
> lattice parameters, bulk moduli... E.g. you want an eq. lattice
> parameter converged to better than .1 a.u, a bulk modulus converged
> to better than 3-4%, and phonons converged to better than 1%.
>
> 2) for pseudopotentials, the defaults you should probably use are the
> http://qe-forge.org/gf/project/pslibrary/ (we keep a compiled version
> of all the pseudos here http://theossrv1.epfl.ch/Main/Pseudopotentials)
> or the GBRV high-throghput library http://www.physics.rutgers.edu/gbrv/
> (just be careful that this latter might have elements with very large
> numbers of semicore electrons - listed here in a very cool manner:
> http://theospc12.epfl.ch/GBRV_map/css3d_periodictable_GBRV.html )
>
>
>                         nicola
>
>
> ----------------------------------------------------------------------
> Prof Nicola Marzari, Chair of Theory and Simulation of Materials, EPFL
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